Filament activating means



Dec. 19, 1933. H. s. POLIN 1,940,184

FILAMENT ACTIVATING MEANS Filed Aug. 19, 1950 minal thereof.

Patented Dec. 19, 1933 FILAMENT ACTIVATIN G MEANS Herbert S; Polity-San Francisco, Calif., assignor to Polin, Inc New York; N. Y., a corporation.

of Delaware Application August19, 1930. Serial No. 476,392

7 I Claims-'- This invention is a method for'controlling the activation'andiheating of the filament ofthea usual vacuum tube;

Thefilament of: therordinaryivacuum tube is heated bythe'A'batterywhich has to be switched on manually when the deviceis-torbe used, and which should be-switched'ioif;when..the tube is no-longerz in use. In contradistinction to this, and accordingxto this-invention, a circuit arrangement is'providedwhereby voice or other modulations impressed on the microphone transformer gcircuit automaticallycause the heating of the :filament; and" whenv the modulations cease; the heating .of.;.the filament. ceases.

This is effected by an. arrangement of the circuit :in: such manner: that impressions of the voioe or -other characteristic on the microphone. cause the circuit to function as a switchxand permitsthe-completion: of the filament circuit "duringthe period of the. impression of the modulationsxon the microphone.

More specifically; in .one embodiment of the inyention there isprovidedacross the filament circuit 'a gas filledidischarge tube of the- Geiss ler type, which may." be filled with some gas as argon, krypton-helium: or the like. 7

This gas filled tube-when subjected to alter nating current, will permit the passage through it of the current from the :A battery and through the'rfilament. When subjected to high orlow frequency oscillations which are present in the microphone transformer-circuit, it becomes conductive and permits the flow of current from the A battery through the filament. As soon as these oscillations cease, the gas in the tube becomes non-conductive again.

The gas filled tube shunts the filament circuit, and is preferably connected across the primary of the microphone transformer.

Another embodiment of the invention eliminates the use of a gas filled tube by introducing the filament current directly into the microphone transformer with the filament and filament power source in series with one input ter- In this way the diaphragm of the microphone, by the impression of characteristics on it, completes the filament circuit, thereby activating the filament and permitting activation of the tube.

I have found that a. source voltage considerably greater than the rated filament capacity of the tube is required for proper filament activation because of the short duration of the closed circuit, activated directly by the impression of voice characteristics upon the microphone diaphragm. Under test conditions where the rated filament voltage of the tube was two volts, six volts were necessary, to produce proper activa* tion. However, this ratio would differ with the type of microphone used and could more properly be computed by comparison of the amper age draw of the microphone, the primary of the microphone transformer and the-filament of the tube used.

This invention is not limited to use with one tube, but may be used with a plurality of tubes.

In the drawing .illustrating possible embodiments of the invention,

Fig. 1 shows thepreferred way of carrying, out the invention, i

Fig. 2 shows another wayvof carrying out the inve'ntionwith a three element tube.

Fig. 3 shows another way of carrying out the invention.

Referring now to the drawing; showing a simple circuit in which the control element and' plateof-a thermionic discharge device T areassociatedwith both means for impressing modulations on. the control device and means for. translating; said." characteristics, a microphone 1 having'usual primary transformer 2 and secondary 5ihas one. terminal of the input connected itothe terminal of the filament 3 of the thermionic discharge device T, the other terminal of .which'is connected through source of currentiito one terminal of the microphone. Shunteddacross the two transformer input terminals with: which theifilament terminals .are in. circuit is a gas filled discharge tube '7, preferably of the Geissler type. A condenser 6 may be bridged across the microphone, for preventing arcing during switching. Oscillations in the secondary 5 of the transformer are impressed on the grid through conductors 5a and 5b, a variable condenser 50 being inserted in this circuit for obtaining clarity of tone, condenser 50 acting to filter out undesirable oscillations, outside of the normal band of the microphone secondary.

Conductor 13 and battery B complete the plate circuit.

In operation, voice or other modulations impressed on the microphone 1 set up oscillations in tube 7 which make it conductive, thereby completing a circuit from power source 4, through conductors l0 and 11, tube 7, conductor l2 and filament 3. However, while most of the current apparently passes through tube 7, some of it is shunted through the primary 2 of the microphone transformer, through the microphone 1 and conductor 12 to filament 3.

When the voice modulations cease, substantially no currentpasses through the filament 3.

Figure 2 shows a three element tube 15, the filament of which is in circuit through conductors l6 and 17 with battery 18 and the primary 19 of microphone 20. Conductor l4 and battery B complete the plate circuit. In this arrangement, the activation of the filament is directly efiected by voice modulations impressed on the microphone. The microphone diaphragm acts as a switch and carries the full current during activation. A small condenser 6' across the microphone prevents arcing during switching.

Figure 3 illustrates the connection of a relay 22 across the output circuit of the microphone transformer 23. The passage of alternating current into the output 24 of the transformer as a result of the impression of signal characteristics on the input of the transformer, effects the closing of the relay which has an independent power source 25 and an armature 26-whichcompletes the filament circuit for such period as alternating current is present in the secondary, that is, when voice or other modulations are present in the primary circuit of the transformer.

I claim as my invention:

-1. Filament activating means for a thermionic discharge device comprising in combination with the usual filament and current source therefor, a transformer, the primary of which is in series with the filament, means for'impressing modulations on the input circuit of the transformer, and means associated with the transformer and with the filament circuit, for passing current through the filament from its current source only when modulations are impressed on the input of the transformer. 1

2. Filament activating means for a thermionic discharge device comprising in combination with the usual filament and current source therefor, a transformer, the primary of which is in series with the filament, means for impressing modulations on the input circuit of the transformer, and means associated with the input and output of the transformer, and with the filament circuit, for passing current through the'filament from its current source only when modulations are impressed on the input of the transformer.

3. Filament activating means for a thermionic discharge device comprising in combination with the usual filament and current source therefor, of a microphone, a microphone transformer, the

primary of which is in series with the filament, and means associated with the filament current and with the microphone transformer circuit for passing current through the filament from its current source only when modulations are impressed on the microphone transformer.

4. Filament activating means for a thermionic discharge device comprising in combination with the usual filament and current source therefor, of a microphone, a microphone transformer, the primary of which is in series with the filament, and means associated with the inputv and the output of the microphone transformer, and with the filament circuit, for passing current through the filament from'its current source only when modulations are impressed on the microphone transformer circuit.

5. Automatic means for the activation of the filament in a thermionic discharge device, having the usual power source in circuit with the filament, the combination of a' microphone, and a microphone transformer, the primary of the transformer being in series with the filament and its power source, whereby currents set up in the primary of the transformer pass through the filament and heat it.

6. In combination with a thermionic discharge device having the usual filament and power source therefor, a microphone, a microphone transformer, the primary of the transformer being in circuit with the filament and its power source, and an element'in shunt across the aforementioned. circuit which is normally non-conductive, but which becomes conductive when voice or other modulations are impressed on the primary of the transformer, and transmits current from the filament power source for heating the filament.

T7. In combi ation with a-thermionic discharge device having the usual filament and power source therefor, a microphone, a microphone transformer, the primary'of the transformer be ing in circuit with the filament and .its power source, and an element'having the characteristics of a Geissler tube, in shunt across the aforementioned circuit which is normally non-conductive, but which becomes conductive when voice, or other modulations are impressed on the primary of the transformer, and transmits current from the filament power source for heating the filament.

HERBERT S; POLIN. 

